In many electronic applications, it is desirable or even required to protect electronic circuitry from tampering. Tampering with electronic circuitry or an electronic module involves unlawful or unauthorized access to the module with the intention of retrieving, altering, or adulterating sensitive information in a product, a package, or a system. The product, package, or system may be a point of sale terminal, a payment terminal or cash dispenser for use with bank cards, an authentication terminal for use with smart cards containing identity data and other personal information, a cryptographic module, and so forth. Security countermeasures against tampering involve secured physical features (such as a closure or casing) that make unauthorized access to a protected object or protected electronic module more difficult.
The detection of tampering can entail detection of an attack on these secured physical features. For example, the security of the electronic module may include a tamper detector for detecting interference with one or more detection circuits that secure access to the physical features. A detection circuit may include electrical conductors whose continuity is interrupted by tampering. Alternatively, the electrical detection circuit may have switches that are designed to open or close if the secured physical feature (e.g., closure) is opened or otherwise breached. By way of example, a detection signal may be applied via an output element of the tamper detector to one end of a detection circuit of the physical security feature. An incoming signal can be received at an input element of the tamper detector from the other end of the detection circuit. The tamper detector can compare the original detection signal with the incoming signal in order to detect interference with the detection circuit. However, continuous improvements are needed for circumventing attempted attacks on secured electronic modules.